Glycerol 3-(2,2,2-trichloroethyl) carbonate

ABSTRACT

1,2 and 2,3-Diacylglycerols are prepared from sn-glycerol 1,2acetonide via the intermediate sn-glycerol 1,2-acetonide 3(2,2,2-trichloroethyl) carbonate, which, after hydrolysis with acid to the 1,2-diol derivative rearranges stereospecifically in pyridine or thermally to give sn-glycerol 2,3-carbonate.

United States Patent Pfeiffer et al. 1 1 June 20, 1972 [541 GLYCEROL 3-(2,2,2- [56] References Cited TRICHLOROETHYL) CARBONATE TED STATES PATENTS [7 Inventors: F i n m n- ;J m 2,266,591 12/1941 Eckey etal. ..99 163 Weisbach, Cherry Hill, both of NJ. [73] Assignee: Smith Kline & French Laboratories, OTHER PUBLICATIONS Phlladelphla. Rakhit et al., Canadian J. Chemistry, Vol. 47, No. 15, pp. 221 Filed: Sept. 17,1970 2906 2910 8/1/69 [21] Appl. No.: 73,225 Primary Examiner-Lewis Gotts Assistant Examiner-Diana G. Rivers Related PP"="" Attorney-William H. Edgenon, Richard 1). Foggi Joan [63] Continuation-impart of Ser. No. 722,538, April 19, Keps,Alan Lowrie and Joseph Mflrlino 1968, Pat. NO. 3,558,656.

57 ABSTRACT 52 us. 01 ..260/463, 260/3402, 260/3409, and are Prepared fmm sn'g'yceml 2 0/403 2 0 4 0 260/611 A acetonide via the intermediate sn-glycerol 1,2-acetonide 3- [511 1m. 01. ..C07c 69/00, C07d 13/04, C07C 69/30 (2.214richloroelhyl) cafbmater which hydmysis with [58] Field of Search ..260/40s,463 acid to the L derivative rearranges slereospecifically in pyridine or thermally to give sn-glycerol 2,3-carbonate.

1 Claim, No Drawings GLYCEROL 3-(2,2,2-TRICHLOROETHYL) CARBONATE This application is a continuation-in-part of copending application Ser. No. 722,538, filed Apr. 19, 1968 now US. Pat. No.-3,558,656.

This invention relates to new chemical compounds and to a 5 X P F for P p Sald compounds- In Particulal, the In the formula X, R may be a saturated or unsaturated t1 f fi g yf esters and to P f aliphatic group of nine to 19 carbon atoms. Among the groups f P' Product35133:t of Invention f I which are therefore encompassed by the RC0 designation are 2 g; 2' 9""; and useful compound sn'glyceml LZ-acetomde l 0 capryl, lauroyl, myristoyl, palmitoyl, stearoyl, arachidoyl, omethyl) carbonate A-decylenoyl, A dodecylenoyl, palmitoleoyl, oleoyl, elaidoyl, ricinoleoyl, petroselinoyl, vaccenoyl, linoleoyl, linolenoyl, and arachidonyl. It is preferred that both acyl 0 groups be the same, although selective acylation by known (L methods permits the preparation of compounds having dif- C a 0- H ferent acyl groups.

H 0 0 Congo C13 The process aspect of the invention consists of a method for H preparing sn-glycerol 2,3-carbonate (lV) through hydrolysis of sn-glycerol l,2-acetonide-3-( 2,2,2-trichloroethyl) A second product aspect of the invention consists of the 20 CH3 CH2 CH 0H novel and useful compound sn-glycerol 3-(2,2,2- 2 trichloroethyl) carbonate (Ill). 1. 11 U-CH C143 \0 QH .5. Base or 11ml 07. 0/ CHzOH Cmocoocmccu (hum HO H n carbonate (ll) with a weak acid and rearrangement to IV by HOCOOCHQLCIK means of thermal or base catal sis. The referred h drol tic Y P y Y system consists of boric acid and trimethyl borate. Tempera- A third product aspect of the invention consists of the novel wres from approximate), to reflux F of the and f l compound smglycerol l'2 carbonate 3 (2,22 solvent may be used, the length of t|me required being approxtrichloroethyl) carbonate v rmately inversely proportional to the temperature. Temperatures of 80-l00 for about 2 hours are preferred in the boric acid-trimethyl borate system to effect the rearrangement.

/ a 35 Generally, temperatures of about 65-l50 are effective to 1 cause the rearrangement. A base such as pyridine may also be OCH used.

(EHQOCOOCHNCIS Another useful system consists of first hydrolyzing [I with v dilute hydrochloric acid in a solvent such as methanol-ether at 40 room temperature and then cyclizing to IV with a base such as A fourth product aspect of the invention comprises the pyridine or by heating (-l50). Temperatures of about novel and useful sn-l,2-diacylglycerol 3-(2,2,2-trichloroethyl) 35 may be employed in the hydrolysis, room temperature carbonate compounds X. These compounds constitute a most being preferred.

Important aspect of the invention, as they permit the first The invention in all its aspects is made clear by reference to facile preparation of polyunsaturated 1,2-diglycerides. the chart below (JH7OH CH: OCH: CH; O--CH CHzUll ()(1Il l C ----v C HO(|JH 0 C \O- H Cg; \O- VH CHQOCOUCII2CC13 \U 3H:

HaQH (EHOCOOOHiCCl! I II 111 IV ?H2OC2 o-cm 0=CH1 (:mocon o-cn t 0: 0:0 RCOO?H 0:

\O H \O- H CHzOCOOCHICC]: O-UH2 dmOH dmooooomcols VI V X XI CHzOH CIIaOCOR CPlzOCOR CHzOH HO(l)H RCOOSIH RCOOCH RCOO H CH30C3 CHzOCdza UHzOH CHzOCOR VII VIII IX XII omor'on ucoodu mocoocmccn,

Compound II is prepared by treatment of sn-glycerol 1,2- acetonide (I) with 2,2,2-trichloroethyl chloroformate in the presence of an acid acceptor such as pyridine. This novel intermediate is converted to sn-glycerol 2,3-carbonate (IV) by means of a weak acid, e.g., H 80 followed by heating at 65? l50. The rearrangement is stereospecific and results in theelimination of trichloroethanol and acetone. sn-Glycerol 3-(2,2,2-trichloroethyl) carbonate (III) is also obtained in the reaction, this product being the expected hydrolysis product of II. Vacuum distillation of III also produces IV, with the elimination of trichloroethanol. When the reaction mixture containing III and IV is treated with triphenylmethyl chloride in the presence of an acid acceptor such as pyridine, the known sn-glycerol 2,3-carbonate l-triphenylmethyl ether (XI) is obtained. This compound is then converted by known methods to 2,3-diacyl-sn-glycerols, including the 2,3- distearate, 2,3-dioleate, 2,3-dilinoleate, and 2,3-dielaidate which are preferred. These products are optically active and can alternatively be designated as L-2,3-diacylglycerols or D- 1,2-diacylglycerols.

Compound XI is converted to the diacylglycerols by hydrolysis of the carbonate group with alkali, acylation with two equivalents of an acyl halide such as stearoyl chloride, and removal of the triphenylmethyl ether grouping with boric acid and trimethyl borate. The rearrangement of compound II to give compound IV thus enables one to readily prepare the 2,3- diacyl-sn-glycerols XII in six steps.

The present invention also provides a means for preparing the enantiomeric 1,2-diacyl-sn-glycerols IX, alternately designated as D-2,3-diacylglycerols or L-l,2-diacylglycerols. Compound II is hydrolyzed in strong acid, preferably in IN hydrochloric acid and the resulting sn-glycerol 3-(2,2,2- trichloroethyl carbonate) III is then acylated with an acid ha lide such as stearoyl chloride to give the sn-glycerol 1,2- distearate 3-(2,2,2trichloroethyl) carbonate X. Removal of the trichloroethyl carbonate group with zinc and.acetic acid gives the diacylglycerol IX.

An alternative method of obtaining these sn-l,2-diacylglycerols (IX) involves the reaction of compound [II with phosgene to give sn-glycerol 1,2-carbonate 3-(2,2,2- trichloroethyl) carbonate (V). Removal of the trichloroethyl carbonate group with zinc and acetic acid gives the sn- I ,2-carbonate VI. Formation of the 3-triphenylmethyl ether and hydrolysis of the carbonate with alkali gives compound VII. Diacylation as previously described gives VIII and removal of the triphenylmethyl group give the products IX.

The present process thus provides a method for obtaining both of the optically active 1,2-diacylglycerols by means of a limited number of reactions starting with the novel common intermediate II. The advantages of the process are readily apparent from the recognition that the intermediate sn-glycerol l-triphenylmethyl ether 2,3-carbonate (XI) was previously obtainable only from D-mannitol in a l2-step sequence and the intermediate sn-glycerol l,2-carbonate 3-triphenylmethyl ether was previously obtainable only from a multistep sequence using sn-glycerol-3-benzyl ether as an intermediate. The present process obviously requires many fewer steps. It is especially advantageous in preparing diacylglycerols in which the acyl groups are unsaturated, as previous methods have required cumbersome and lengthy procedures involving protective groups.

The diacylglycerols obtained by means of the present process and from the novel intermediates of this invention are known to be used as emulsifying agents, particularly in the food industry, and as coatings for pharmaceutical products. They are used in the preparation of baked goods and in superglycerinated shortenings. They are used as coating materials for various food products such as meat, fish, and cheese in order to protect them against loss of moisture and against contamination. Their manner of use is well-known to those skilled in these fields.

The diglycerides are also known to be involved in the synthesis, metabolism, and deposition of body fat. They are useful in preparation of phosphatidic acids and phospholipids, the latter compounds being an important class of body lipids. The availability of optically active diacylglycerols provided by means of the present process is of significance in these areas.

The following examples are intended to illustrate the preparation of the compounds of the invention and the prac tice of the process of the invention, but are not to be construed as limiting their scope. Temperatures stated are in degrees Centigrade.

EXAMPLE I sn-Glycerol-l ,2-acetonide 3-( 2,2,2-trichloroethyl) carbonate To an ice cold solution of 62.3 g. (0.471 mole) of snglycerol 1,2-acetonide in 25 ml. of dry CHCl was added slowly 50 ml. ofdry pyridine. Then a solution of g. (0.471 mole) of 2,2,2-trichloroethyl chloroformate in 50 ml. of CHC1 was added dropwise at 0. The solution was stirred overnight at room temperature, diluted with 400 ml. of ether and washed successively with dil. HCI, water, 5% NaHCO and water. After drying (Na SO the solvent was evaporated and the colorless syrup was distilled to afford l l8.5 g. (82 percent) of the title compound, b.p. l30/0.025 mm; [01],, l.5 (c 0.87, CHCI nmr CDCI 3)84.8l (s, 2, CH CCI Found: C, 35.35; H, 4.39,

EXAMPLE 2 sn-Glycerol 2,3-carbonate l-triphenylmethyl ether A solution of 4.65 g. of sn-glycerol-1,2-acetonide 3-( 2,2,2- trichloroethyl) carbonate, 2.0g. of boric acid, and 20 ml.. of trimethyl borate was refluxed for 1 hr. under a nitrogen atmosphere. Then the mixture was heated on a rotary evaporator at 80 for 40 minutes, and cooled and diluted with ml. of water and 300 ml. of ethyl acetate. The resulting suspension was swirled in a separatory funnel until all the solids have dissolved. The ethyl acetate layer was washed with brine, dried (Na SO concentrated and azeotroped with benzene to afford a viscous syrup. Glc analysis of the product (as the trifluoroacetate derivatives) showed the material to be a mixture of 74.3 percent of sn-glycerol 3-(2,2,2-trichloroethyl) carbonate and 25.7 percent of sn-glycerol 2,3-carbonate.

The crude product was dissolved in 15 ml. of CHCl and 10 ml. of pyridine and 4.21 g. of triphenylmethyl chloride was added; the solution was stirred at 60 for 18 hours. Ethyl acetate was added and the solution was washed with dil. HCI water, 5% NaHCO, and water. The dried solution was evaporated to give a white solid which was crystallized from acetone-petroleum ether to yield 3.7 g. (68 percent) of the title compound, m.p. 2l5-217. Additional recrystallization from acetone gave the analytical specimen, m.p. 2l7-2l9; [a],, +l9.1(c I.33,CHCI;,).

Anal. Calcd for C H O C, 76.65; H, 5.59

Found: C, 76.58; H, 5.66

EXAMPLE 3 sn-Glycerol l,2-carbonate 3-(2,2,2-trichloroethyl) carbonate A solution of l 1.1 g. of sn-glycerol-l,2-acetonide I i-(2,2,2- trichloroethyl) carbonate, 20 ml. of ether, 6 ml. of methanol, and 3 ml. of 3 N l-ICl was stirred at room temperature for 18 hours and then evaporated in vacuo at 30 to give an oily residue, the oil was dissolved in 300 ml. of ethyl acetate and washed with brine (6x). The dried solution was concentrated and azeotroped with benzene to give a colorless, viscous syrup which was a mixture of 93.5 percent of sn-glycerol 3-(2,2,2- trichloroethyl) carbonate and 6.5 percent of sn-glycerol 2,3-

carbonate. This mixture was dissolved in 50 ml. of dry pyridine and a stream of phosgene was introduced over the top of the stirred solution (kept at After 3040 minutes, during which time a solid precipitated, the reaction was cautiously quenched by the addition of ice, then diluted with 200 ml. of ice-water and the solid extracted into ether. The ether solution was washed with dil. HCl, water, NaHCO and water. Removal of the ether gave 10.4 g. of an oily white solid which was crystallized from ether to afford white, crystalline sn-glycerol 1,2-carbonate 3-(2,2,2-trichloroethyl) carbonate, m.p. 7779. An analytical sample was recrystallized from isopropanol, m.p. 80-82; [M 105 (0 1.16, CHCl nmr (CDCl 84.80 (s, 2, CH CCl Anal. Calcd for C-,H Cl -,O,,: C, 28.65; H, 2.40; Cl,

36.24 Found: C, 29.01; H, 2.42", Cl, 36.45

EXAMPLE 4 sn-Glycerol 1,2-distearate 3-(2,2,2-trichloroethyl) carbonate Crude sn-glycerol 3-(2,2,2-trichloroethyl) carbonate (5.34 g.) was dissolved in ml. of dry CHCl and 4.5 ml. of pyridine. To the cooled solution was added dropwise a solution of 12 g. of stearoyl chloride in 50 ml. of CHCl The solution was stirred for 48 hours at 25, diluted with e ther and washed with dil. HCl, water, NaHCO and water, dried (Na SO and concentrated to a white, oily solid. Tlc showed the product to be contaminated with some sn-glycerol 1- stearate 2,3-carbonate. This mixture was chromatographed over Florisil with ether-petroleum ether mixtures to give 9.7 g. (60%) of homogeneous sn-glycerol 1,2-distearate 3-(2,2,2- trichloroethyl) carbonate, m.p. 55-56. Recrystallization from ether-methanol gave the white, crystalline analytical sample, m.p. 56S7; [11],, 1.7 (c 1.05, CHCl nmr (CDCl 84.76 (s, 2, CH,CCl

Anal. Calcd for C,,H,,Cl,0,: C, 63.02; H, 9.70;

CI, 13.29 Found: C, 63.53; H, 9.66; CI,

Found: C,

Also prepared by the same procedure was s n-glycerol 1,2- dilinoleate 3-(2,2,2-trichloroethyl) carbonate; [01],, 3.28 (c 1.49, CHCl nmr (CDC1,)84.80 (s, 2, CH CCI Anal. Calc'd for C H Cl,O C, 63.66; H, 8.78;

CI, 13.42 63.25; H, 8.77;

Found: C,

In a similar fashion there may be prepared sn-glycerol 1,2- dielaidate 3-(2,2,2-trichloroethyl) carbonate and other 1,2- diacyl-sn-glycerols.

EXAMPLE 5 sn-Glycerol 1,2-distearate A suspension of 1.0 g. of sn-glycerol 1,2-distearate 3-(2,2,2-

trichloroethyl) carbonate 1,0 g. of activated zinc, 15 ml. of

glacial acetic acid and 15 ml. of ether was stirred at room temperature for 3 hours. The zinc was filtered off and the filter cake washed with ether. The filtrate was washed with NaHCO solution and water, dried, and evaporated and the crystalline residue crystallized from methanol and then from ether to afford pure sn-glycerol 1,2-distearate, m.p. 73.5-74.5; [01],, 26 (0 1, CHCl C, 74.94; H, 12.26 Found: C, 75.14;H, 12.19

Anal. Calcd for C H,,O,:

EXAMPLE 6 sn-Glycerol 2,3-distearate l-triphenylmethyl ether A solution of 1.2 g. (3.59 mmol) of sn-glycerol l-triphenylmethyl ether (prepared by NaOH hydrolysis of sn-glycerol 2,3-carbonate l-triphenylmethyl ether as described in J. Chem. Soc. 1967, 431), 2 ml. of pyridine and 10 ml. of CHCIQ was cooled in ice and a solution of 2.17 g. (7.18 mmole) of stearoyl chloride in 10 ml. of CHCl was added dropwise. The solution was stirred for 48 hours at 25, diluted with ether and washed with cold 0.5 N HCl, water, 5% NaHCO and water. After workup there was isolated 4.2 g. of crude product which was chromatographed over 160 g. of Woelm alumina (Act 111) with petroleum ether as eluent. Crystallization from petroleum ether-methanol gave 2.25 g. (73 percent) of pure snglycerol 2,3-distearate l-triphenylmethyl ether, m.p. 51.5- 52.5. The analytical sample from petroleum ether had m.p. 52.553.5; [M 12.2 (c 0.99, CHCI Anal. Calc'd for C H O C, 80.32; H, 10.46

Found: C, 80.60; H, 10.55

EXAMPLE 7 sn-Glycerol 2,3-dioleate l-triphenylmethyl ether C, 80.69; H, 10.04 Found: C, 80.56; H, 9.97

Anal. Calcd for C,,H O,,:

EXAMPLE 8 sn-Glyccrol 2,3-distearate A mixture of 300 mg. of sn-glycerol 2,3-distearate 1- triphenylmethyl ether, 300 mg. of boric acid and 6 ml. of trimethyl borate was refluxed for 3 hours, then heated on a rotary evaporator for 30 minutes at The orange syrup was partitioned between ethyl acetate and water, and the organic layer was washed with water and then dried and concentrated to an oily solid. Tlc showed the crude product to be a mixture of mostly 1,2-diglyceride with a trace of 1,3-diglyceride, some tripenylmethylearbinol and triphenylmethyl methyl ether. A crystallization from methanol removed the triphenylmethyl derivatives and another crystallization from hexane gave pure sn-glycerol 2,3-distearate, m.p. 72-73.5; [01],, 2.5 (c 1.2 CHCl The 2,3-dioleate was obtained using the same procedure described for the distearate except that the crude product (an oil) was chromatographed over Florisil impregnated with percent boric acid, and using hexane and hexane-ether mixtures as the eluting system. The triphenylmethyl impurities were removed in the first few cuts, and the small amount of 1,3-diglyceride was eluted before the pure dioleate was obtained; [01],, 2.14 (c 5.62, CHCl The 2,3-dilinoleate, 2,3-dielaidate, and other 2,3-diacylates are prepared in a similar manner.

EXAMPLE 9 sn-Glycerol l,2-carbonate 3-triphenylmethyl ether To a cooled solution of 4.0 g. of sn-glycerol 1,2-carbonate 3-(2,2,2-trichloroethyl) carbonate in ml. of acetic acid and 15 ml. of ether was added 4.0 g. of activated zinc dust and the suspension was stirred at room temperature for 3 hours. The inorganic materials were filtered off with the aid of ether and the filtrate was evaporated at water aspirator vacuum, and then with a vacuum pump (0.02 mm, pot temperature less than 40). The crude syrupy sn-glycerol 1,2-carbonate was dissolved in ml. of dry CHCland 10 ml. of pyridine, and 3.8 g. of trityl chloride was added, After stirring overnight at the solution was diluted with ethyl acetate and worked up in the manner described in Example 2 to give 2.0 g. (53 percent) of sn-glycerol 1,2-carbonate 3-triphenylmethyl ether, m.p.2l7219;[a 1,,- l7.5(c 3.97, CHCl Anal. Calcd for C,,H, 0 C, 76.65; H, 5.59 Found: C, 76.53; H, 5.60

EXAMPLE l0 sn-Glycerol 1,2-distearate sn-Glycerol 1,2-carbonate 3-triphenylmethyl ether is hydrolyzed with NaOH to sn-glycerol 3-triphenylmethyl ether by the procedure of J. Chem. Soc. 1967, 431. This compound is then treated with 2 equivalents of stearoyl chloride in pyridine and chloroform according to the procedure of Example 6 to give sn-glycerol 1,2-distearate 3-triphenylmethyl ether. The triphenylmethyl group is then removed with boric acid and trimethyl borate according to the procedure of Example 8 to give sn-glycerol 1,2-distearate.

sn-Glycerol 1,2-dioleate, sn-glycerol l,2-dilinoleate, snglycerol 1,2-dielaidate, and other sn-glycerol 1,2-diacylates are prepared in the same manner by acylating sn-glycerol 3- triphenylmethyl ether with 2 equivalents of oleoyl chloride, linoleoyl chloride, elaidoyl chloride, or other acyl chlorides, respectively, and then removing the triphenylmethyl group.

EXAMPLE 11 sn-Glycerol-2,3-carbonate A solution of 12.68 g (0.0475 mole) of sn-glycerol-3-(2,2,2- trichloroethyl) carbonate in 15 ml of dry pyridine was stirred at 60 for 18 hours. The solvent and trichloroethanol were evaporated at 55 (0.02 mm), ethyl acetate was added, and the solution was washed with small volumes of dil. HCl, water, Nal'lCO and brine. The ethyl acetate was dried and concentrated to the syrupy sn-glycerol 2,3-carbonate. This material can be purified via the triphenylmethyl derivative (see Example 2) or by distillation: b.p. (0.15 mm); [01],, 27.84 (in substance).

Anal. Calcd for C,H,O C, 40.68; H, 5.12

Found: C, 40.44; H, 5.15

sn-Glycerol-2,3-carbonate can also be prepared from snglycerol-3-(2,2,2-trichlorethyl) carbonate by vacuum distillation of the diol.

I claim: 1. A compound of the formula CHzOH HO H 

